The present invention relates to the field aeronautic propulsion. It relates to a system for changing the pitch of blades of a propeller driven by a turbine engine, and in particular means for supplying fluid to a control means of said pitch change system. The invention also relates to a turbine engine equipped with such a pitch change system.
The change of pitch or variable calibration of blades of a turbine engine propeller is one way for improving the performance and output of turbine engines under different flight conditions.
Turboprops, for example with pairs of despun propellers, referred to by the expressions “open rotor” and “unducted fan”, equipped with these pitch change systems are known. Turboprops differ from turbojet engines by the use of a propeller outside the nacelle (unducted) instead of an internal fan. The pitch change system may also apply to a turboprop with a propeller or adapt indifferently to several propellers.
In a turboprop of the open rotor type, a gas-generating part and a propulsion part are aligned and arranged in a stationary cylindrical nacelle supported by the structure of the aircraft. The gas-generating part can be arranged in front of or behind the propulsion part. The gases circulate in the turboprop from upstream to downstream. The propulsion part includes a pair of coaxial and despun propellers, upstream and downstream, respectively, that are rotated in opposite directions relative to one another by a turbine, in particular a low-pressure turbine, of the gas-generating part via a reduction gear, for example a planetary gear set. The propellers extend substantially radially across from the transmission shaft with a longitudinal axis to the outside the nacelle. In general, each propeller comprises a substantially cylindrical rotary case carrying an outer polygonal hub received rotatably around the longitudinal axis in the stationary nacelle. The hub includes radial cylindrical housings distributed on its periphery around the longitudinal axis. Shafts, with radial axes, here perpendicular to the longitudinal axis of the turbine engine, secured to roots of the blades, are received in the housings of the polygonal rings and extend toward the inside of the turbine engine.
An example system for changing the pitch of each propeller is known from document WO2013/050704. In FIG. 2, this pitch change system 23A is installed in the core of the rotary parts of a turbine engine, such as that shown in FIG. 1, for example with an annular control cylinder 25A rotating the roots of the blades. The annular control cylinder 25A includes a cylinder 27A mounted on a stationary case 13A and a piston 29A movable relative to the cylinder 27A. The movable piston 29A is connected to a connecting mechanism 26A, which is connected to each shaft 47A with a radial axis. The cylindrical rotary case 11A rotates around the stationary case 13A. To that end, at least one bearing 12A is arranged between the stationary case 13A and the rotary case 11A. The system further comprises means for supplying fluid to the annular control cylinder allowing the movable piston 29A to move relative to the cylinder. The movement of the movable piston 29A following the fluid command of the annular control cylinder 25A ensures the desired angular pivoting of the blades by the connecting mechanism 26A by pivoting the radial shafts 47A connected to the blades.
However, such an architecture consisting of converting power arriving from the stationary part of the stationary nacelle into movement on the rotating part of the turbine engine presents many difficulties. One of the difficulties lies in the dimensioning and the integration of the various elements into this rotating part. This in particular applies to the integration of the supply means of the control cylinder. One solution consists of using hydraulic channels made from piping that connect to the moving piston on the one hand, and the stationary nacelle on the other hand. Axial systems can also pass through the shaft of the propeller in the case of a single propeller. The integration of these piping or axial systems is complex, since they must be fastened both to the stationary and rotary parts, and must account for the small amount of space in and around the control cylinder. Furthermore, the control cylinder is subject to substantial radial forces from the rotary part that involve deformations of the control cylinder as well as sealing problems that are inevitably passed on to the supply means thereof. These forces are multiplied when the control cylinder is such that it plays a structural role.
The present invention in particular aims to propose supply means of the control means, in particular, of a system for changing the pitch of blades of a turbine engine propeller, taking into account the difficulties of integration in a cluttered environment.